The trial of Neumann and Sass (; ), also known as the Kaunas Trials, was the among largest mass trials of Nazis in the early 1930s. The trial resulted in the convictions of the leaders of regional Nazi parties, Theodor von Sass, and other party members for their activity in the Klaipėda Region.
The trial process was held in the Palace of Justice and the Parliament. Some of the trial's 69 hearings were held as a public trial upon invitation, despite requests from Nazi Germany and urging from the states of the Entente to organise a secret trial, at the Lithuanian Palace of Justice and the Parliament, in Kaunas, in 1935. The trial drew attention across Europe and was attended by many international journalists. The convicted Nazis were sentenced to death or to penal labour by the Court of the Lithuanian Armed Forces. Following an appeal, the Supreme Tribunal of Lithuania left the court's judgment and verdict unchanged. Foreign pressure made Lithuania later grant amnesty to all convicts before they had completed their sentences, and none of the executions was carried out.
Background
The Klaipėda Region was detached from East Prussia, in the German Empire, by the Treaty of Versailles in 1919 and became a mandate of the League of Nations under provisional French administration until a more permanent resolution could be worked out. Lithuania acquired the region after the Klaipėda Revolt of 10–15 January 1923, which had been carried out mainly by soldiers and volunteers from Lithuania. According to Lithuanian intelligence, about 60% of the region's population supported an uprising, about 30% were neutral and only about 10% supported a free state.
The Klaipėda Region consisted of four administrative territorial units: the city of Klaipėda and the counties of Klaipėda, Šilutė, and Pagėgiai (about 5% of the territory of Lithuania). A Lithuanian census carried out in the region in 1925 found its total population was 141,000. The census classified inhabitants by declared language as 43.5 percent German, 27.6 percent Lithuanian and 25.2 percent "Klaipėdan" (Memelländisch). Lithuanian and German authors argued about whether the Klaipėdians (Memellanders) were Lithuanian or German, and the Lithuanian government believed they were Germanized Lithuanians.
However, by tradition, the population of the region generally supported Germany, rather than Lithuania. German politicians promoted a Memellander ideology and argued that Germans and local Lithuanians were "two ethnicities (Volkstümer), yet one cultural community (Kulturgemeinschaft)". In 1924, the Klaipėda Convention between Lithuania, the United Kingdom, France, Italy and Japan was signed. It guaranteed the autonomy of the region within Lithuania. The convention also granted the right for the residents of the region to decide on citizenship. After an agreement between Lithuania and Germany in February 1925, German citizens were allowed to depart to Germany. In 1925–1933, 17,730 people departed from the Klaipėda Region.
Lithuania's acquisition of the Klaipėda Region damaged the region's economy and resulted in growing unemployment and local hostility towards Lithuania. German nationalists began to take advantage of the situation, which worsened over time.
On 6 April 1923, strikes and demonstrations, organized by nationalists and communists, began in the region. At night, unidentified activists demolished monuments of Kaiser Kaiser Wilhelm I and Borussia which had symbolized German culture and statehood in the region. The German population of the region considered that to be a Lithuanian provocation, but Lithuanians denied.
Another obstacle to the Lithuanian government's plans to Lithuanize the region and its population was the Klaipėdans' (Memellanders') opposition to the government and their support for pro-German parties in the elections to the Parliament of the Klaipėda Region (). Moreover, the Germans had considerable influence in all government bodies. The anti-Lithuanian activities in the region were heavily financed by various German financial institutions. According to Klaipėda Governoe Antanas Merkys (1927–1932), the deteriorating situation of the region was dangerous in 1927, and in 1930, school curriculums classified Lithuanian as a foreign language, which was seldom studied.
On 29 June 1931, Joseph Goebbels participated in an event in nearby Tilsit and claimed that the aim of the National Socialists was for the Klaipėda Region to be ceded to Germany as part of the restoration of the pre-war German borders. This rhetoric was supported by the Nazi press.